Display devices such as liquid crystal display devices generally have a backlight on the backside, the side opposite the display screen. A known display device has, for example, a light-diffusing layer and a prism on the display screen side of the backlight in order to improve luminance of the display screen.
A recently known backlight for display devices has a wavelength conversion layer containing semiconductor particles to convert light wavelength. In such a backlight, white light is provided through several wavelength conversion processes (for example, see Patent Literatures 1 and 2).
However, in the case of producing white light through such a wavelength conversion layer, the luminous efficiency may be insufficiently improved depending on the type of the semiconductor particles in the wavelength conversion layer or the light-diffusing layer formed on at least one surface of the wavelength conversion layer. Particularly, when the display device has a wavelength conversion layer containing optically isotropic semiconductor particles and a light-diffusing layer containing ultrafine particles with a size of the order of nanometers as diffusing particles, the light energy conversion efficiency of the entire backlight is not significantly improved.
Another known display device has a wavelength conversion layer containing diffusing particles to achieve improved light energy conversion efficiency.
However, for a display device with such a diffusing particle-containing wavelength conversion layer, more materials need to be dispersed in the binder component of the composition for producing the wavelength conversion layer. This increases the number of factors to consider upon dispersion, such as semiconductor particles, diffusing particles, and other particles, and binder components. This may complicate the production of a wavelength conversion layer capable of providing desired properties.
Moreover, since the wavelength conversion layer is relatively thick, addition of diffusing particles throughout the wavelength conversion layer increases its haze. Even though the addition of diffusing particles increases the light energy conversion efficiency, such an increase in haze may decrease the amount of light from the wavelength conversion layer toward the display screen.